The invention is concerned with the prevention of scale deposits on solid surfaces in contact with hard water containing hardness scale-forming ions and with the preparation of compounds or compositions which are effective for this purpose. In particular, the invention is concerned with scale prevention in natural brines on ferrous metal walls and other solid surfaces, especially in oil producing and waterflood systems.
Inorganic polyphosphates have long been the most effective and economical sequestering agents used for the prevention of scale deposits in both oil producing and water flood systems. However, due to the problems encountered in feeding inorganic polyphosphates and their incompatibility with many waters, a need for a liquid organic phosphate with good solubility in waters containing hardness ions has become increasingly evident. For this reason, a liquid product with good solubility in produced waters and having the effectiveness and low treating cost of inorganic polyphosphates is needed.
In U.S. Pat. No. 3,462,365 and in U.S. patent applications Ser. No. 600,354 filed Dec. 9, 1966, now U.S. Pat. No. 3,479,956, and Ser. No. 857,239, filed Sept. 11, 1969, now U.S. Pat. No. 3,620,974 organic phosphates have been described which fulfill this need. It would nevertheless be desirable to provide other organic phosphates which are effective for this purpose.